Target for reactive sputtering and film-forming method using the target

#The present invention relates to a target for use in reactive-sputtering for forming a titanium nitride thin film which is to work as a barrier metal for a semiconductor device, and a method for forming a film from the target.

#The integration of LSI has been remarkably improved in recent years, and the width of a circuit pattern line is accordingly becoming much finer. LSI has a diffusion-preventing layer formed to prevent the reaction diffusion between aluminum forming electrodes and silicon forming elements. With the circuit pattern line width becoming finer, this diffusion-preventing layer is also required to have a smaller thickness and further required to have a high melting point highly sufficient to prevent the diffusion. Further, since the diffusion-preventing layer constitutes part of an electrode, it is preferred to select a material therefor from materials having lowest possible, specific resistance. A titanium nitride layer is presently attracting attention as a material having a high melting point and low specific resistance and having a remarkably excellent diffusion-preventing effect.

#The above titanium nitride layer is formed by a reactive sputtering method using pure titanium as a target (Monthly Semiconductor World, 1992, 3p56). In this reactive sputtering method, an impact is applied to a target of pure titanium by means of charged particles of an nitrogen ion and an argon ion formed by glow discharging, whereby not only the target is nitrided, but also titanium nitride particles are released by the force of the impact to form a titanium nitride film on a silicon wafer opposed to the target.

#FIG. 1 shows the integrated intensity ratio of crystal phases of samples obtained in Example 1 when the maximum peak in X-ray diffraction was taken as 100%.

#FIG. 2 shows the integrated intensity ratio of crystal phases of samples obtained in Example 1 when the maximum peak in X-ray diffraction was taken as 100%.

#FIG. 3 shows a change in the film-forming rate with regard to a sputtering power when a target of Sample No. 10 according to the present invention was used.

#The present invention will be described further in detail by reference to prior art.

#In a conventional reactive sputtering method using a target of pure titanium, pure titanium atoms present on a target surface and a film surface and nitrogen introduced as an atmospheric gas are ionized and allowed to react by a plasma impact. As shown in a treatise on thin solid films by D. K. Hohnke, D. J. Schmatz and M. D. Hurley, 118, 1984, the reaction scheme in the above method is greatly influenced by reactive sputtering conditions, and particularly rate-determined by conditions for introducing reactants. It is therefore greatly depends on the flow amount of gas being introduced into a sputtering apparatus, the composition of the gas, the gas pressure for forming a film and an electric power being inputted to a target (hereinafter referred to as sputtering electric power) which influences the amount of sputtering particles to be released from the target. These factors respectively show dependency having hysteresis with regard to the composition of a thin film.

#The sputtering electric power is explained as one example. In reactive sputtering using a target of pure titanium, when a specific power value is reached while increasing the electric power, there is obtained a film having an intended composition. When the electric power goes up for some reason, the result is that the same composition cannot be achieved even if the electric power is reset at the same power value as before by decreasing the electric power.